Improved grain size homogeneity, enhanced piezoelectric and mechanical properties of potassium sodium niobate-based ceramics

The development of high-performance potassium sodium niobate (KNN)-based piezoceramics for next-generation transducer devices is essential for a sustainable society. However, apart from remarkable piezoelectrical properties, considerable momentum should also be paid to preferable mechanical properties for the reliable operation of electronic devices. Herein, a novel three-step sintering technique is proposed in this study to modulate grain growth behavior, leading to simultaneous enhancement of piezoelectric and mechanical properties. Our research reveals that abnormal grain growth of KNN-based piezoceramic can be effectively inhibited by manipulating the thermal homogenization process at an appropriate temperature (900 degrees C) in the first stage of the three-step sintering technology. A homogeneous grain size alleviates grain boundary stress caused by abnormal grains, inducing not only superior piezoelectric properties (piezoelectric coefficient [d(33)] = 430 pC/N and planar electromechanical coupling factor [k(p)] = 0.61) but also excellent mechanical properties (Young's modulus [E] = 161.15 GPa, nanoindentation hardness [H] = 7.56 GPa, and average compressive strength = 70.59 MPa). This work provides an effective paradigm for further optimization of both piezoelectric and mechanical properties robustness of lead-free piezoelectric ceramics for industrial applications.